E-nose job

Environmental scientists at Lancaster University have discovered that ‘electronic noses’ can be used as a tool to diagnose diseased or damaged plants.

Electric noses, or e-noses, mimic the human sense of smell using sensors that respond to airborne chemicals by producing an electronic signal. E-noses have already been shown to be able to sniff out human diseases such as TB, off-flavours in food and even mouldy books in libraries.

Researchers at Lancaster have now shown that an electronic nose can tell when crop plants such as tomatoes, cucumbers or capsicum pepper plants are being attacked – and even diagnose between different types of damage.

Their findings show that an e-nose can tell the difference between a plant that is being chewed by caterpillars and one that is infested by spider mites. It can also distinguish between a crop being attacked by pests as opposed to infected by a disease.

The system could become an early-warning system in glasshouses, alerting farmers and growers to the first signs of pests and diseases, allowing control measures to be taken long before crop yields are affected.

Dr Nigel Paul, of Lancaster University’s Environment Centre, said: ‘We all know that many plants have distinctive smells, which are due to a cocktail of volatile organic compounds [VOCs].

‘We know that these volatile cocktails change subtly when plants are under attack and that some insect predators use the change in volatiles as a message to detect pests that make a good meal.

‘We wondered if we could “eavesdrop” on this using an e-nose, allowing us to differentiate between different VOC cocktails too.’

The Lancaster team grew cucumbers, capsicum peppers and tomatoes in a glasshouse for five weeks, before placing hungry tobacco hornworm caterpillars or spider mites on their leaves. They also infected some of the plants with a fungus that causes powdery mildew disease.

A Bloodhound electronic nose, supplied by Scensive Technologies in Normanton, UK, was used to analyse the air stream flowing over each group of plants.

Results showed that the electronic nose could distinguish the healthy aromas from each of the three species of plant. More impressively, it could distinguish whether a plant had been attacked by a caterpillar, or mite, or infected by mildew.

Dr Paul added: ‘Farmers and growers have been successful in reducing pesticide use and increasingly use sustainable approaches to pest and disease control but such controls work best when attack is detected and treated early.

‘Early detection has usually relied on skilled growers walking their crop to spot the first signs of damage, but our work suggests that e-nose might be an alternative to this.

‘E -noses are a fast-moving technology and instruments available now are much more sensitive than the one we used in these experiments, so the next step is to see how newer instruments can be deployed in a crop environment.’

The research was funded by the Horticultural Development Company and a Royal Society Dorothy Hodgkin Postgraduate Award.